The disclosure relates generally to ceramic precursor batch compositions and more particularly to ceramic precursor batch compositions and batches for forming ceramic honeycombs.
In the formation of ceramic bodies, e.g., silicon carbide, cordierite, mullite, alumina, or aluminum titanate bodies, plasticized mixtures of various inorganic powder batches are prepared which are then formed into various shapes. These plasticized mixtures should be well blended and homogeneous in order for the resulting shaped body to have relatively good integrity in both size and shape, and uniform physical properties. These mixtures typically further include organic additives such as binders, plasticizers, surfactants, lubricants, and dispersants as processing aids to enhance cohesion, plasticity, lubricity, and/or wetting, and therefore to produce a more uniform batch.
Cellulose ethers have been used as extrusion binders to impart plasticity while imparting good drying behavior. While other ceramic binder systems can also be used for ceramic extrusion, cellulose ethers such as methylcellulose (MC), hydroxypropylcellulose (HPMC) and hydroxyethylmethylcellulose (HEMC) can form high temperature gels. The gelling behavior facilitates rapid drying while preventing distortions that can occur with other binder systems as they are heated.
Certain types of ceramic honeycombs, such as substrates for automotive catalytic converter systems, need to meet a variety of performance characteristics. Such requirements not only affect the types of materials that can be successfully combined to make the ceramic honeycombs but also the geometry of the honeycombs. For example, demand for substrates having very thin webs (i.e., less than 2.5 mil (0.0025 inch, 0.0635 mm)) has dramatically increased. Manufacturing such structures entails many technical challenges, including the fact that such manufacture typically involves the use of screens and dies having smaller open areas that can more easily become plugged. Such plugging is undesirable and can not only result in the need for frequent part or equipment replacement but can also at least temporarily shut down an entire production line.
Decreasing the particle size of inorganic raw materials used in the batch compositions can help to reduce the propensity for screens and dies to become plugged. However, there is a continued need to minimize this occurrence, particularly in the manufacture of ceramic honeycomb structures having very thin webs.